Posted
by
Soulskillon Sunday December 11, 2011 @12:22AM
from the back-to-the-drawksssh-sstthhhhkkk-zzzttt dept.

Freddybear writes with this quote from BusinessWeek:
"Philip Falcone's proposed LightSquared Inc. wireless service caused interference to 75 percent of global-positioning system receivers examined in a U.S. government test, according to a draft summary of results. ... The tests worked off an 'extraordinarily conservative' threshold and didn't show the devices' performance was affected, [LightSquared exec Martin Harriman said]. 'If we're affecting the performance of the device — my goodness, we'd like to be sure that doesn't happen,' Harriman said. The laboratory testing was performed for the National Space-Based Positioning, Navigation, and Timing Systems Engineering Forum, an executive branch body that helps advise policy makers on issues around GPS. It found that 69 of 92, or 75 percent, of receivers tested 'experienced harmful interference' at the equivalent of 100 meters (109 yards) from a LightSquared base station."

I'm not saying Republicans are angles or anything like that. I am saying this a very bad case of corporate ties directly to the whitehouse that is threatening to disrupt a major technology just to make some money...

If it interfered with GPS, they'd get caught awfully fast and LOSE a lot of money. Interfering with GPS doesn't just mean that someone's turn by turn directions get messed up. A lot of things now depend on GPS, mostly for the time information.

Solyndria (another company propped up by the white house despite many reports saying the company was not financial viable) was given a ton of money, which the founders (also heavy donors to the Democratic party) got a lot of, then the company went bankrupt but they left with a few million dollar paychecks.

It doesn't matter if the company folds. Just that Philip Falcone makes money in the process, which he will.

The strange thing is that he's got a userid number around mine, which says that he's been here at least ten years. How can you go use a website for over ten years, without picking up that the moderation system is capricious, random, and certainly grounded in groupthink -- but corrupt? "Corrupt" is one of the few negative terms I wouldn't use to describe Slashdot's moderation system. One of the few actual advantages that it does have is that it's not corrupt. Even if Apple or Microsoft started paying people to mod up comments that praised them, there'd be outraged people downmodding those comments just as quickly.

I think people attach too much significance to karma and moderation, anyways. It's pathetically easy to game the system (just pander to whatever the prevailing groupthink is on a subject... or brazenly challenge the prevailing groupthink and say, "I'll probably get modded down for this, but..."). When I first started on Slashdot, I was an unrepentant karma whore, just to see how high I could get my karma. Then they hid the number, which killed that game. I've never had a (Score 5: Troll) comment, though, and I've always wanted one of those. Maybe some day... a boy can dream.

Well, what he said was that the moderators can't handle the truth. Then, in the next sentence he mentioned corruption which I inferred to mean that whether the corruption is in the DNC or the RNC, it shouldn't matter to the moderators.

Even if Apple or Microsoft started paying people to mod up comments that praised them, there'd be outraged people downmodding those comments just as quickly.

I don't know about that, downmodding can be suicide. I used to receive mod points almost every two weeks until I downmodded an obvious WP7 astroturf and got bitchslapped by the moderation system and haven't seen points in over a year. The moderation system may not be corrupt but it is badly broken.

Now, now, the party of purple is equally corrupt in both its left and right branches. They only differ on what kind of corruption they specialize in.

But don't worry, come 2012, you'll get to pick which candidate from the party of purple you prefer, then spend the next 4 years crying yourself to sleep at night, because you know that no matter who is elected, it will be more of the same. And it will be same for your children, and your grand-children, and your great grand-children, who will work for less money that you earn on a Friday afternoon right now, and have less throughout their lives.

Remember to eat your bread and visit the circus on your way home. It's good bread, if a little stale, and the circus has giraffes. Repeat after me: "I live in the greatest country in the world! I worship authority! If I am struck, I will not strike back! The wiretaps are there for my freedoms, which everyone else on the planet is jealous of, and wants to take from me! USA! USA! USA! USA!"

And please explain to me how the millions that were given to Solyndra come close to comparing to the billions that Bush and his Republican mates gave to the contractors to carry out the wars in Iraq and Afghanistan. At least Solyndra did not result in thousands of dead Iraqi and Afghani along with burning through the good will we might have had from the rest of the world after 9-11.

Remember that the Democrats and Republicans actually cooperated on a few things in the 90s, created a pretty good economy and had us showing a surplus paying down the debt, then Bush came in and all the changed. Bush even insisted that the entire Iraq war was and emergency that shouldn't show up in the normal budget, kind of disingenuous don't you think.

No he lined the pockets of his buddy contractors. To the tune of billions. And all of it as emergency appropriations not as part of the regular budget. Republicans didn't have a problem with the deficit when the money was going to their buddies.

On the upside, the Military has just found an new way to jam the GPS of enemies on the battlefield.

On a more serious note, WTF, that has to be some serious bleed over. Almost all of the frequencies used by GPS are reserved government frequencies. Light Squared will use 1525-1559 MHz according to what I have found. The nearest GPS freq is 1575.42 MHz but is the L1 freq explaining why so many receivers get jammed completely. Light Squared has a serious engineering problem, because they either produce nasty sub-carriers outside there assigned frequencies, or they just ignore their assigned frequency and use more bandwidth that they have be allocated.

This link is to the a great Freq. Allocation Chart for the US. While it says 2003, it still applies to this case.http://www.ntia.doc.gov/files/ntia/publications/2003-allochrt.pdf

My reading was that the GPS receivers were picking up the 1552-1559 MHz signal due to being made with cheap parts. That would correlate quite well with the finding that only 3/4 of the receivers were affected - if Light Squared were transmitting out of their assigned band, you'd expect 100% of the receivers to suffer interference.

It's not that they're using "cheap parts". It's that the signal from those little solar-powered tin cans whizzing around in the sky is so weak that adding a notch filter to increase selectivity would significantly affect the ability to receive the signal at all. And they want to drop this elephant right next to it.

if you overload the RF amp, you're screwed. That's probably what's happening. The front ends on consumer GPS units were not engineered to deal with a high-power signal 25 MHz away. It is theoretically possible to engineer GPS receivers that can withstand that, but none have been built yet. So if LightSquared goes live, 75% of consumer (and possibly commercial) GPS units will have serious problems.

Still, this will go through like grass through a goose, the taxpayers will get screwed, and most existing GP

If you had been following along, you would know that consumer GPS units are not affected. That has already been resolved when LightSquared agreed to hold off using the upper band for a period of time, allowing most consumer GPS units to be replaced by normal obsolescence. Their use of the lower band will only affect precision GPS units.

If I was in to conspiracy theories, I'd say that little fact is left out of news articles intentionally to rile up the general population against LightSquared.

Looking at it as someone who has been following this for months, and has no stake in the game either way, it looks more like this; precision GPS manufacturers didn't feel the need to filter a band in between two that they were using since it wasn't really being by anything with any power, and it could have cost them a few more pennies per unit. And then LightSquared managed to somehow get the FCC to consider opening the band to terrestrial transmitters. Now it's a multi-billion dollar pissing match. Nobody is completely right, and nobody is completely wrong.

Very close but not quite. The L1C signal is not a simple continuous carrier like the old transit sats from the 50s/60s. The data rate is somewhere around ten megabits and it modulation is BPSK. The exact answer requires more detail but the actual transmitted BW will end up maybe 10 megs higher and 10 megs lower than the center theoretical carrier. Which is getting uncomfortably close to the lightsquared signal.

So... that's 1565 or so, vs the interference at 1559. So you head over to minicircuits.com (a seller of many microwave components, including the high pass filter you are trying to purchase) and look for a coaxial filter with a curve showing almost 0 dB attenuation at 1565 and up to keep your noise figure usable, and at least 60 dB out of band attenuation at 1559. Then you realize why the EE types claim "its a law of physics" that this simply cannot be worked around. Oh and note the ones that don't even come close to making the grade are roughly the size weight and cost of a very small cell phone. Generically building a filter in that frequency range with those specs is impossible, but building the device to that exact frequency spec and stable over any temperature range makes it even more impossible.

Before the sorta knowledgeable DSP types jump in, yes, you can get filter curves like that using DSP. However you need a analog input clean enough to do the DSP on it... So, again, you're screwed. Just plug your 60 dBm 3rd order IMD preamp into your 32 bit A/D 10 GHz A/D converter and then process it. This is technobable of the finest level, components with specs like that Might exist in just 50 years or so, but they sure don't now.

Good explanation, thanks. this makes me ponder whether Lightsquared might do better to go to an Ultra Wideband technology, which IIUC would eliminate nearly all interference problems, and would also provide nearly ultimate privacy protection against third parties snooping the signal. (Which might make the 'official' snooper-types uncomfortable.) It would certainly make Lightsquared a disruptive technology, a generation ahead of anyone else.

Tis interesting that an Executive Branch office would make such a report to him so soon after this news was leaked... you'd think the White House would have better control over the SEC... the same way it does the NLRB, EPA, or DOJ (oh I look forward to Holder going over F&F (though he should have never been given the job)).

The bureaucracy has a certain very real independence from the government. That can be a problem when the administration is trying to accomplish worthwhile things, but it can also serve as a check on corruption in the government, even if in turn corruption in the bureacracy is a huge problem in itself. Wheels within wheels.

It's a sad commentary when good things come from parts of the system working at cross purposes, but it works.

It's a sad commentary when good things come from parts of the system working at cross purposes, but it works.

I don't know; I see it as similar to a RAID array: every drive I purchase will fail, but by arranging my activities correctly, I will never lose data. Similarly, corruption may be present in all areas of government, but by arranging it just right it has made it more than 200 years. Current trends seem to indicate it won't make it to 300.

Then you'll need to get your information somewhere besides hotair.com.

When a reputable news source reports this, it will mean a lot more.

TFA is from Business Week. The HotAir.com article only quotes from Business Week and includes other relevant facts that seem well sourced.I'm not sure how the GP ended up talking about Republicans, but this was reported by a reputable news source.

I understand that, but the Business Week article doesn't say anything like the text SuperKendall used in his link to the HotAir article.

This is done all the time. Someone wants to make a political point. They link to some blog's hit piece article which links to a reputable article which does not make the same conclusion and then viola! a = c.

Then you'll need to get your information somewhere besides hotair.com.

I knew someone would get all huffy about that.

See, here is the issue. I would love to link to a more "reputable" source than HotAir, because some predjudiced people cannot look beyond a name at facts. But that leads us to a HUGE problem:

There isn't another source, even though there SHOULD be.

The facts of the matter are very clear are they not? The interference with the GPS, proven. The donations of Philip Falcone to the Democratic Party, well documented [guardian.co.uk] and public.

And yet WHO in the "reputable" media made this very easy and very pertinent connection for us? Is that not in fact the very role it is vital for the media to play, as watchdog for just this kind of ultra-slimy influence peddling? This is the easiest story in the world to find evidence to show to us all, and yet only Hot Air and other "fringe" media bothers to make the simplest of connection.

The real problem is that the "reputable" media is utterly lost to partisan concerns, death afraid that "their side" may lose something. I truly respect the role the media plays in shining light on the doings of politicians everywhere, and welcome weeding out corruption. But you cannot weed only looking at half the garden.

So until the point when the "real" media decides to start acting like JOURNALISTS again, I'm afraid you'll have to suffice with information from reputable sources linked together by media you obviously despise - because no-one else is doing that job. I would argue you should probably look at the facts of the matter rather than who is pointing them out; I can discern truth both on HotAir and on HuffingtonPost as required. If you were smart you would seek to do the same rather than get lost in the echo chamber.

I have no political ties to LightSquared but considering they're trying to blanket the nation in broadband... I'm really hoping they resolve these interference issues as well. Not because I voted for Obama but because I want to see technology succeed. I also want to see white-space succeed which is another initiative the Obama white-house has advocated for. Again, not because of my voting registration but because I agree with their stated agenda of increasing access to highspeed internet.

See, here is the issue. I would love to link to a more "reputable" source than HotAir, because some predjudiced people cannot look beyond a name at facts.

Please. Hotair was the "news source" that broke the story that the President's birth certificate was a phoney because the PDF file had layers. Let me think...oh, they broke the story about how there's a secret tape of Michelle Obama using the word "whitey" (well, they didn't actually break the story, but they rode it hard over the course of about a year

I'm an electrical engineer. I did my doctorate in a GPS lab working on safety-of-life applications (landing planes and such). The LS issue has been a very hot topic of discussion in the technical community for most of the past year. At the annual ION GNSS conference this past September, there was a panel discussion on the preliminary test results described in TFA. Out of approximately 600 people in the room, there were exactly two who expressed opinions supporting LS's contention that the interference to GPS would be insignificant: one guy was the LS General Counsel, and the other was a guy who is claiming he has retrofit kits (RF notch filters) that will eliminate the interference. It should be noted that, when asked how his kits would be fitted to the millions of GPS receivers already in the field, the latter person had absolutely no answer.

It is not at all a stretch to say that very nearly 100% of the people who have done LS testing, or evaluated the results from an engineering perspective, conclude that the effects as proposed will be somewhere between "significant" and "catastrophic."

other was a guy who is claiming he has retrofit kits (RF notch filters) that will eliminate the interference. It should be noted that, when asked how his kits would be fitted to the millions of GPS receivers already in the field, the latter person had absolutely no answer.

Run the numbers on the Q factor required and the maximum possible passband attenuation to keep the noise figure of the front end usable... If you know what "snake oil" is WRT crypto it sounds like this guy's offering sounds suspiciously like "frequency grease" WRT RF.

Note that if the problem is front end overload, his snakeoil/freqgrease might be a simple 10 dB attenuator, probably being sold at an immense markup. If would be easier to duct tape aluminum foil to the existing antenna until the incoming signals are knocked down enough that the FE is not overloading but optimistically there is still enough RF signal left to decode.

This is assuming its not at the RF technology level of those stickers you put on cell phones to magically do things that sound good.

Run the numbers on the Q factor required and the maximum possible passband attenuation to keep the noise figure of the front end usable... If you know what "snake oil" is WRT crypto it sounds like this guy's offering sounds suspiciously like "frequency grease" WRT RF.

Note that if the problem is front end overload, his snakeoil/freqgrease might be a simple 10 dB attenuator, probably being sold at an immense markup. If would be easier to duct tape aluminum foil to the existing antenna until the incoming signals are knocked down enough that the FE is not overloading but optimistically there is still enough RF signal left to decode.

This is assuming its not at the RF technology level of those stickers you put on cell phones to magically do things that sound good.

I am intimately familiar with the RF arguments. The proposed notch filter is indeed snake oil, but not for reasons of insufficiently steep stopband rolloff. Rather, it's a relatively bulky thing which will work just fine for the receivers produced by the guy's company (Javad), and maybe even other receivers that could be retrofitted. But it is totally unusable for most embedded receivers (handhelds, etc.) due to size (and cost), and there are a lot more of those deployed in the world. The "snake oil" part of the argument is that he is being spectacularly disingenuous about it: when asked how he intends to retrofit every TomTom, Garmin, GPS-enabled wristwatch, and mobile phone already out there in the field, he just waves his hands and says, "those devices won't be affected."

While I'm on the subject, people seem to be unaware of a further bit of deception on LS's part. Their initial proposal included two bands just below GPS (the so-called "Low 10" and "High 10"). When testing showed that the resulting interference would make the proposal a non-starter, LS submitted a modified proposal in which they would only the lower of the two bands (farther away from GPS), and at a lower broadcast power level. The thing is, LS never stated that this was their intended final configuration. Indeed, upon further discussion, it emerged that this revised proposal was intended only to placate objections in the short term, and that LS fully intends to use both bands and the higher power levels (as in their original proposal) eventually. In other words, the potential interference problem was never addressed, just kicked down the road a bit.

In short, the proposed filter was far more sophisticated than the bits of aluminum foil you might see for sale on QVC on channel 179 at three in the morning... but it's virtually meaningless in any practical sense.

You are probably referring to Javad Ashjaee. The guy is a GPS authority, with a long track in contributions to the community. He founded a few companies, the latest one Javad, which creates high quality precision receivers. He is someone who until two months ago, I would have never doubted. But then he started contradicting himself with his message. First, he started to complain how lightsquare does affect his receivers. Then he proposed ending the P-code as a way to mitigate for this (http://www.gpsworld.c

This is the worst idea yet. Worse than broadband over power lines, worse than that idea about using gas pipes. I thought the whole point to discontinuing analog TV service and freeing up that bandwidth was to provided wide area Internet. *facepalm*

I thought the whole point to discontinuing analog TV service and freeing up that bandwidth was to provided wide area Internet. *facepalm*

The point to discontinuing analog TV service was to be able to sell off bandwidth to private companies who wanted it and were lobbying for it. Just another case of Americans being sold out again by their government.

I find it very odd that people believe that any criticism of the Obama administration has to be accompanied by a statement proclaiming that Republicans are bad, even when it's completely irrelevant to the topic being discussed. It's almost as if, for some weird reason, people think they have to apologize for making very valid and necessary criticisms against the terrible policies supported by this president.
Not that I give a shit about Republicans, but I think the apologetic tone softens the criticism, wh

I find it very odd that people believe that any criticism of the Obama administration has to be accompanied by a statement proclaiming that Republicans are bad, even when it's completely irrelevant to the topic being discussed.

I think that the GP post is preemptively trying to stop the tidal wave of "but the Republicans did THIS [bad thing]".

I'll admit it softens the tone, but it at least stops some of the noise that was sure to follow.

Were *you* duped? Then you weren't paying attention. While he was running for president he voted in favor of FISA. So you should have known all along that he was lying through his teeth. But he was probably still the best of two bad choices. (And don't talk about the third party candidates. The only plausible reason to vote for any of the ones I investigated was that they had no reasonable chance of being elected. Nobody sane will invest the time and effort required to run as a third party candidate.

The Federal Election Commission has no record of Phil Falcone, a registered Republican, nor LightSquared Chairman and CEO Sanjiv Ahuja of having ever contributed to President Obama’s political campaigns.

Among the issues being raised is if political contributors received favorable treatment by the Obama administration. Since 2007, a key investor in LightSquared, Phil Falcone, has donated $85,500 to Republicans and $50,500 to Democrats.

One of the big issues is that those giant combines and harvesters on farms use GPS, so the farming industry is upset http://westernfarmpress.com/government/lightsquared-threat-gps-even-filters [westernfarmpress.com]
Lightspeed owns the bandwidth adjacent to GPS, but the GPS devices are still affected by transmission on lightspeed's bandwidth.
So it isn't really "lightspeed zmog destroy teh GPS" by doing some dastardly deeds, it is them trying to use the bandwidth they purchased and older GPS devices not able to handle the interference (even tho they are class B and must not create interference and must accept interference). Airplanes are another issue with interference. http://macsblog.com/2011/02/should-i-worry-about-gps-jamming/ [macsblog.com]
really, though, just a clash of the lobbyists in washington on who has to pay extra to make lightspeed able to use their bandwidth

Yes, but the towers are broadcasting signals that are orders of magnitude more powerful to ground receivers than the gps satellites. If Lightspeed was a satellite phone system (so if it was another satellite system producing the crosstalk), it would not interfere even if the frequencies were directly adjacent.

I'm not an expert, but read some back issues of GPS World. Lightsquared is doing dastardly deeds - this frequency was never intended for terrestrial broadcasting. They pulled a fast one and got this for a steal. The FCC screwed up big time - either incompetence or someone was asked to do a favor or paid off. There's a lot of FUD - Lightsquared has been planting stories claiming that the GPS devices won't work do to shoddy engineering. The facts are that they should be building terrestrial base stations that broadcast near GPS frequencies and not have to at least go through a thorough review and pay what this spectrum is really worth.

You don't see consumer electronics or their suppliers companies publicly complaining because it's not in their best interest to show a weakness at this time. e.g. if company A says that this will impact them, then company B can use that statement when they pay a visit or market to A's customers.

Fortunately this only impacts the good old USA. The rest of the world can continue to reap the benefits of GPS while they ramp up their systems. (Glonass has been on the rise. Galileo is finally making progress. Compass is on its way and hopefully they will eventually publish their ICD.)

Read more of those issues, or read Inside GNSS: this does indeed impact Galileo and it impacts anything within 600 miles of US borders, which means it impacts intercontinental aviation.

In a letter filed yesterday (July 19, 2011), Heinz Zourek, director-general for enterprise and industry, wrote to FCC Chairman Julius Genachowski that if LightSquared is allowed to begin broadcasting in the band, “What are now neighbour MSS [mobile satellite service space-to-Earth] transmissions at similar receive powers to RNSS [radionavigation satellite service such as GPS and Galileo] would in future be many orders of magnitude higher and with the potential to severely disrupt reception of RNSS signals.”

He cited analysis — including ESA studies —carried out in Europe that showed interference effects to Galileo equipment would occur from 100 meters to almost 1,000 kilometers (620 miles), “depending on the type of receiver being used.”

I'll leave it to the tin-foil crowd to speculate on why the FCC is only getting around to publishing its findings now. I'd suggest, though, that what they come up with might not be so paranoid after all in this case. Those who want to dig through some glaring evidence of bipartisan corruption will find it without looking too hard into this story, because the shady deals were conducted practically in the open on this one, from the SkyTerra days on through the past week. The Republicans are already working overtime on trying to assemble a timeline of Falcone's dealings with Obama: if the Democrats were smart, they'd have a team doing the same to show Republican connections, because they are there too (SkyTerra got permission for this back in the Bush era).

The fact that this story is dying in the back pages while Lindsey Lohan's Playboy spread and the circus clowns that have hijacked the Republican nomination get near-orgasmic coverage is a sad comment on how useless journalism has become.

They might be allocated the bandwidth, but this means they are responsible for interference. Of course they probably respect the FCC requirements, but they still need to consider interference, aqnd this one is an obvious case. Transmitting 42 dBm or so a few MHz away from a band such as GPS, and that on the scale of a nation IS a bad case of interference.

I expect the project to fail anyway because the handset manufacturers have no way to implement that band in a suitable phone with GPS.This means expensive hardware in each compatible phone. Did you look at the RF HW of a typical phone ? it's a spagetti of PAs and filters. This band would mean passing from 2 RF paths to 3, 50% price increase. Furthermore, putting another antenna is hopeless, and the phone will jam it's own GPS, if available. Nobody in the industry wants such a monster, except Lightsquared.

For civilian GPS receiver, who are more sensitive due to a design nore vulnerable to interference (first LNA before the first filter), they will be affected. GPS performance will be unacceptable in some places close to antennas, and probably compatible handsets operating in the vincinity will affect them also.

It's very unlikely to be lightspeed signal bleeding over out of their channel. That is reasonably easy to control, and it would show up in 100% of tested receivers. More likely, this is "adjacent channel interference". It is much harder to get a receiver to reject signals in adjacent channels. It takes a difficult/expensive to construct filter. If you go back to the old days of television, you'll note that you don't find adjacent channels allocated in major markets, for instance, because in the early days it was essentially impossible to build a receiver that could reject a strong signal on an adjacent channel. So here we have a case of a receiver looking for a very weak signal, and on an adjacent channel there is a strong local transmitter that you are trying to reject. I'm no surprised that there are issues. Also, because GPS has up till now not had strong nearby, adjacent signals to reject, it could actually be that the first mixer is getting overloaded, so the damage is done before you even get to the first IF filter.

It is much harder to get a receiver to reject signals in adjacent channels. It takes a difficult/expensive to construct filter. If you go back to the old days of television, you'll note that you don't find adjacent channels allocated in major markets, for instance, because in the early days it was essentially impossible to build a receiver that could reject a strong signal on an adjacent channel.

If these frequency channels have been defined and allocated since before good filters existed,how come the channels were never adjusted to reflect the reality in the air?

It just seems like a very basic concept to space/allocate the channels in such a wayas to completely eliminate any adjacent channel interference, even if it means not-usingsignificant amounts of frequency (not that they were going to be used anyways)/pardon my ignorance

It's not so much that the nearby frequencies need to be silent. I believe it was actually the case that those frequencies were originally licensed for low-power signals. So when the hardware engineer was designing his GPS receiver circuit, he would use the expected max power that could be licensed for that band in his calculation for determining how many -dB/Octave his filter needs. Now LS comes in and wants to relicense that spectrum for signals of many orders of magnitude more power; the circuits were simply not designed to handle this because such signals were illegal at the time of manufacture.

It's not the hardware engineer's fault that the adjacent bands were "zoned" to be residential and now LS wants to come in and build an airport.

Nope, it's not adjacent channel interference -- the precision positioning people use a correction signal (from a satellite) in L band, below the GPS L1 signal, that is completely swamped by the LightSquared system -- these precision positioning systems, which are also used in highway construction and other large developments as well as in large scale agriculture, are among the systems that the study identified as impossible to make work even with a redesign -- these bands were meant for weak signal reception of satellite signals, NOT for multi-kilowatt ground stations.

And when you talk about adjacent channel, remember that GPS boxes aren't so much receivers as correlators -- and they are working with signals that are effectively below the noise floor -- that's why correlation techniques have to be used. What might be acceptable as adjacent channel in other modes is devastating to correlator-based designs.

OK, I quickly looked over the excellent presentation that you link to. I don't see where it shows a GPS precision-enhancing signal in L-band getting swamped. It *does* show 15 kW (!) terrestrial base stations very near the GPS L1 band having the potential to get past the roofing filter in a GPS, as my previous post was attempting to yak about.

I was under the impression that differential GPS used short-range terrestrial VHF for a localization signal from another GPS receiver looking at the normal GPS sign

He gives a very nice spectrum on slide 4 -- note the little bump at the bottom labeled "Starfire/Omnistar" -- that's the correction signal used by the John Deere precision GPS system, and others, broadcast by Inmarsat III. It's f*ing buried under the proposed LightSquared 10H signal at 1550.2, and still under the skirts of their 10L signal at 1531!

You can't design around that!

ANYTHING carried by Inmarsat III in that band just below GPS L1 is so screwed if LightSquared uses those frequencies!

this is also a pretty clear indication that FCC was bought off at a high level, and their technical types didn't get to look at it -- they would have screamed.

He gives a very nice spectrum on slide 4 -- note the little bump at the bottom labeled "Starfire/Omnistar" -- that's the correction signal used by the John Deere precision GPS system, and others, broadcast by Inmarsat III. It's f*ing buried under the proposed LightSquared 10H signal at 1550.2, and still under the skirts of their 10L signal at 1531!

Yup, that has a nice picture illustrating the problem.

ANYTHING carried by Inmarsat III in that band just below GPS L1 is so screwed if LightSquared uses those frequencies!

this is also a pretty clear indication that FCC was bought off at a high level, and their technical types didn't get to look at it -- they would have screamed.

Yes, that seems to be happening a lot lately. Good, bottom-up technical analysis from FCC engineers get overridden by political concerns. Broadband over Power Lines (BPL) is another egregious example of politics forcing idiotic technical decisions. Spectrum sharing compatibility analysis seems to have been left back in the last millennium some how.

A quick look at their service suggests that they might have been a nice addition to the existing wireless services. We really do need more providers and new technologies. But even a small chance of interfering with GPS is too much.

Maybe one could swap some rarely used military spectrum further from GPS against military spectrum close to GPS. Given that the military complains the loudest and sits on a lot of spectrum, I think it's reasonable to ask them to contribute to a solution.

But THIS news is about HOW they actually got the FCC to switch the space based spectrum adjacent to GPS to be used for a terrestrial based spectrum. The FCC rules were setup to not have a large power ground based spectrum next to a weak space based spectrum. Somehow Lightsquared 'convinced' them to change the rules. So this would be like a race track owner bribing city hall to rezone the houses on the other side of your street to let him put in a drag strip. If you have a problem with the noise of the

They are all for sale. Everyone in the System. Corruption is the one thing which is impossible to design out, because by definition corruption *IS* the undermining of the system. Hari Seldon's Foundation is the only way to fight it, and it can't win by fixing the system. The only way is to tear down the old system and build a new one, like the 1992 revolution in the Soviet Union. It's really sad that human nature is the thing that dooms all efforts at effective governing.

Let's get over the sensationalism and realize the real problem: We had false expectations of GPS and therefore should not have depended on this technology in defense systems.

You do realize that the US military owns the GPS system. It seems to have worked out pretty well for them. Of course, no tech is perfect but I don't understand what you're whining about. It's not like Lightspeed is going to put transmitters in Afghanistan and if some nefarious persons try to block GPS signals with a transmitter well, the military has some nice little tools to solve that problem.

Here's the problem: You can block "Lightspeed" from deploying devices known to cause harmful interference to GPS signals. Big deal. What you can't do is make it "illegal" to jam GPS. Well, you can make it illegal, but it's a matter of enforcement. Expecting it to work 100%, especially in a battle field, is stupid. Your enemy will build GPS jammers by the dozen and hide them all over the place once they realize this is how you guide your missiles.

All I'm saying, is that this is a symptom of a larger problem: depending on easily jammed GPS.

I realize the military will just triangulate and find the jammers. But a jammer just has to hide their equipment in nearby hospitals and grocery stores, and use intelligent timing and antenna arrangements.... they can make triangulation a very difficult and time-consuming operation. And once the devices are found and destroyed, it's another $15 to deploy another one somewhere else.

I think it's a good idea to try and prevent what you can, such as by not certifying equipment that causes harmful interference. But let's not think this is the real problem with GPS...

Actually, it works out pretty well. They jam GPS, and you have piles of missiles that home in on GPS jammers. It's not practical to jam the US military's GPS because you'll run out of jammers (And people willing to turn them on) before the US military runs out of resources.

I realize the military will just triangulate and find the jammers. But a jammer just has to hide their equipment in nearby hospitals and grocery stores, and use intelligent timing and antenna arrangements.... they can make triangulation a very difficult and time-consuming operation.

No, that's not the way it works. "intelligent timing and antenna arrangements" greatly impede the ability to jam, and triangulation is not necessary to destroy it unless you are shooting at it with artillery. As for someone turning a

Let's get over the sensationalism and realize the real problem: We had false expectations of GPS and therefore should not have depended on this technology in defense systems.

Defense systems have had direct P(Y)/L3 acquisition for a while. On a battlefield, they can also eliminate the interference with a HARM if they so choose. And they have inertial guidance and other backup systems for when GPS is being jammed. This isn't about defense; this is about civilian GPS use.

Uhm, blocking GPS functionality is extremely trivial. I assure you, every home in america (and probably most of the first world) has devices that are more than capable of knocking out GPS with only minor trivial changes than ANY RF engineer or EE could do.

It was never designed to be interference free, thats a silly notion in the first place. It is rather impractical to try and block it however, as it takes massive infrastructure to do it over a large area... and well, its basically cutting off your nose

If you fly on airplanes, or live near an airport, you should care [battleswarmblog.com]:

Imagine a Boeing 787 Dreamliner conducting an nighttime instrument approach to Ronald Reagan Washington National Airport when the GPS signal is overwhelmed at a critical phase. Now imagine that same Boeing 787 Dreamliner plowing into downtown Arlington, Virginia at 150 miles per hour, leaving a wake of bloody body parts and burning jetfuel for a quarter-mile.

You are ignorant of the history of the L1 band that GPS and a number of other satellite services occupy. GPS equipment (and their front-end filters in particular) has been designed under the assumption that the surrounding spectrum would only be occupied by satellite communications which have output power many orders of magnitude less than what LightSquared is proposing. It is not the fault of GPS manufacturers that spectrum that has traditionally been used for satellite communications (and it should be con

GPS is *designed* to listen to frequencies outside it's transmission frequency. Ya know why? These satellites are zooming around the earth, causing the received signal on the ground to be different. It's called the Doppler Effect. It's somewhat of an important rule in physics.

LightSquared's spectrum is only licensed for satellite transmission, which is why they were able to buy it so cheaply. And if they used it as such, there would be absolutely no problem! Now they want to use it on the ground at much hig

Then said airlines need to to invest in proper GPS equipment, instead of shit-ass receivers that don't know what the fuck 1575.42 MHz [wikipedia.org] means. LightSquared's licensed spectrum is 1525-1559 MHz, and GPS L1 is 1575.42 MHz.

The trouble is that there's no such thing as a perfect filter - they don't actually cut off all frequencies at the cut-off point, instead their attenuation increases as you get further from it. The unwanted LightSquared signal is so much more powerful than the GPS signals the receivers are trying to pick up that apparently at that distance it's pretty much impossible to filter it out enough to stop the remnant from overwhelming their input stages and interfering with GPS reception.

Falcone is a registered REPUBLICAN and there is no record of any donations to the Obama campaign. Apparently he did make some donations in some congressional races, but the bulk of his donations were to REPUBLICANS.

1575.42MHz is first of all just the carrier frequency. All useful signals have a non-zero band width. Second, GPS receivers are required by design to not filter out adjacent spectrum because the actual received frequency will differ due to Doppler shift.

GPS signals are extraordinarily weak. The cell towers are over 1000 times as powerful as the actual satellites, and the satellites are so much further away, that the LightSpped signal at a GPS device is often a billion times stronger than the GPS signal. Considering how close the frequencies are that means that an incredibly strong filter is needed, and it must be designed to have near zero attenuation of actual GPS signals, since they are so weak already.

GPS receivers have historically been designed assuming that the nearby signals like those in LightSpeed's frequencies would not be substantially stronger than a GPS signal, since that frequency range was reserved for satellite communications. Even if they had been designed with LightSpeed in mind, it is virtually impossible to design a filter that would work and not harm the performance of GPS without substantially increasing the size of the receiver.

I'm honestly shocked that up to 25% of the receivers did not experience any interference. These were probably large receivers that already had excellent filtering, but which would be completely unsuitable for use in say a cell phone.

Simply put, LightSquared should have known that use of high power terrestial base stations could adversely affect GPS receivers and they should have made an effort to see if a work-around was possible before acquiring rights to the frequency bands. Since they didn't, LightSquared management have probably opened themselves up to shareholder lawsuits.

The original allocation for the LightSquared frequencies was for satellite based transmitters and it is up to LightSquared to prove that shifting to terrestial transmitters will not cause harmful interference.